Model for a photoinduced insulator-metal transition in a one-dimensional quarter-filled organic salt: Evidence for a nonadiabatic charge-phonon coupling

Lee, J. D.

doi:10.1103/physrevb.80.165101

Cited by 7 publications

(4 citation statements)

References 30 publications

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“…9 Generation of coherent phonons is also observed in a broad class of the photoinduced insulator-metal transitions (PIMTs) accompanying the structural changes in terms of the melting of the lattice-induced order. [10][11][12] An important profile under debate is that, in a system with strong electronphonon coupling, the photoinduced ultrafast dynamics show unexpected nonadiabatic behaviors of electrons and phonons depending on the photoexcitation condition, [12][13][14][15] which differs from the case of a standard solid for which the electrons obey the Born-Oppenheimer approximation (BOA). 16 The proper understanding of the interplay of electrons and coherent phonons in the fs time range is still unclear.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast optical excitation of coherent phonons in a one-dimensional metal at the photoinduced insulator-metal transition

2011

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Photoinduced insulator-metal transition from the charge-density wave (CDW) ground state in a onedimensional electron system is studied within the nonadiabatic theory of electron-phonon coupling. Ultrafast melting and partial recovery of the CDW and its critical slowing down are found to accompany the cooperative lattice response by an electron-phonon energy transfer on the subpicosecond time scale, which is read out by the nonadiabatic depopulation and repopulation of coherent phonons. Further, electron correlation is described in a self-consistent mean-field theory. In the strong electron correlation, the spin-density wave competes with the CDW and the photoinduced responses of the lattice is found to undergo the nonadiabatic-adiabatic transition.

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Section: Introductionmentioning

confidence: 99%

Ultrafast optical excitation of coherent phonons in a one-dimensional metal at the photoinduced insulator-metal transition

2011

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“…The first step takes place within 100 fs and the photoinduced phase is assigned to the (1010) charge disproportionate phase, as shown in the lower panel of Fig. 1(a) [17][18][19][20][21][22][23][24][25][26][27][28]. The time required for the emergence of the metallic phase is 100 ps [22,23].…”

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confidence: 98%

Coherent dynamics of photoinduced phase formation in a strongly correlated organic crystal

et al. 2014

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The photoinduced phase formation in a strongly correlated crystal (EDO-TTF) 2 PF 6 (EDO-TTF: 4,5ethylenedioxytetrathiafulvalene) is investigated using a 12 fs laser pulse. The formation time is determined as 40 fs with observation of coherence of electron-phonon coupled excited states prior to formation. The temperature-independent dephasing time is determined as ß22 fs up to 180 K and the frequency of phonon oscillation is ß38 THz, corresponding to the intramolecular vibrations in EDO-TTF. The phase formation is coherently controlled by relative-phase-controlled two-pulse excitation.Strongly correlated materials exhibit intriguing phases such as superconductor, Mott insulator, spin liquid, and charge density wave [1]. Competitions between electrons, phonons, and spins in the materials play a key role in creating these phases. Photoexcitation controls this competition and initiates cooperative response resulting in a macroscopic ordering, called photoinduced phase transition (PIPT). In PIPT, electronphonon interactions lead to significant changes in dynamics. Thus, not only pure electronic but also electron-phonon dynamics have attracted considerable attention. Time-resolved optical spectroscopy has been widely used to study the electronic and vibrational dynamics and subsequent PIPT by monitoring the transient changes in optical constants on a femtosecond time scale [2][3][4][5][6]. However, the interactions dominating electronic phases are often inferred indirectly from these measurements.Coherent nonlinear spectroscopy utilizing third-order nonlinear response is a powerful tool to directly investigate interactions and has been applied to reveal ultrafast dynamics in semiconductors [7,8], light-harvesting protein complexes [9][10][11][12], and other functional materials [13,14]. However, this spectroscopy has been applied only to a few strongly correlated materials [15] because their electronic coherence is considered to be too short owing to their strong electron-electron interaction. In this Rapid Communication we have investigated 10-fs time scale dynamics of the strongly correlated organic chargetransfer (CT) complex (EDO-TTF) 2 PF 6 (EDO-TTF: 4,5ethylenedioxytetrathiafulvalene) [16], which exhibits unique PIPT due to strong electron-phonon interactions. We also revealed the formation process of the photoinduced phase * onda.k.aa@m.titech.ac.jp from the phonon-coupled excited state as well as the role of coherences in the excited state.(EDO-TTF) 2 PF 6 undergoes metal-insulator phase transition at 280 K because of its strong electron-electron and electron-phonon interactions and shows (0110)-type charge ordering below the transition temperature [16], where the number in parentheses represent the order of charge for EDO-TTF molecules, as shown in the upper panel of Fig. 1(a). This material exhibits a two-step phase transition triggered by photoexcitation in the low-temperature phase, that is, "insulator"-"photoinduced phase"-"metal" transition. The first step takes place within 100 fs and the photoinduced ph...

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“…14 In contrast to these experimental achievements, theoretical studies on the photoinduced ultrafast oscillations have not been carried out so intensively. [18][19][20] Although some of the authors and co-workers have provided a theoretical description on dynamics of an organic compound ͑EDO-TTF͒ 2 PF 6 , the treatment for the lattice degrees of freedom is limited to a classical one. 18,19 A quantum theory for the same material, 20 where quantized phonons are dealt with, focuses on the slow lattice dynamics.…”

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confidence: 99%

“…[18][19][20] Although some of the authors and co-workers have provided a theoretical description on dynamics of an organic compound ͑EDO-TTF͒ 2 PF 6 , the treatment for the lattice degrees of freedom is limited to a classical one. 18,19 A quantum theory for the same material, 20 where quantized phonons are dealt with, focuses on the slow lattice dynamics. Thus alternative quantummechanical treatment is needed to describe the ultrafast oscillations of excitations with much higher frequencies.…”

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confidence: 99%

Photoinduced coherent oscillations in the one-dimensional two-orbital Hubbard model

2010

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We study photoinduced ultrafast coherent oscillations originating from orbital degrees of freedom in the one-dimensional two-orbital Hubbard model. By solving the time-dependent Schrödinger equation for the numerically exact many-electron wave function, we obtain time-dependent optical response functions. The calculated spectra show characteristic coherent oscillations that vary with the frequency of probe light. A simple analysis for the dominant oscillating components clarifies that these photoinduced oscillations are caused by the quantum interference between photogenerated states. The oscillation attributed to the Ramanactive orbital excitations ͑orbitons͒ clearly appears around the charge-transfer peak.

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Model for a photoinduced insulator-metal transition in a one-dimensional quarter-filled organic salt: Evidence for a nonadiabatic charge-phonon coupling

Cited by 7 publications

References 30 publications

Ultrafast optical excitation of coherent phonons in a one-dimensional metal at the photoinduced insulator-metal transition

Ultrafast optical excitation of coherent phonons in a one-dimensional metal at the photoinduced insulator-metal transition

Coherent dynamics of photoinduced phase formation in a strongly correlated organic crystal

Photoinduced coherent oscillations in the one-dimensional two-orbital Hubbard model

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